AD 2021-14-18 Prompted By The Manufacturer Developing Improved T/R Blades Using Different Materials...

The FAA is superseding Airworthiness Directive (AD) 2011-18-52 for certain Agusta S.p.A. (now Leonardo S.p.a.) Model AB139 and AW139 helicopters.

AD 2011-18-52 required revising the life limit for certain part-numbered tail rotor (T/R) blades, updating the helicopter's historical records, repetitively inspecting each T/R blade for a crack or damage, and depending on the results, replacing the T/R blade. This AD was prompted by the manufacturer developing improved T/R blades using different materials and establishing life limits for each improved blade. This AD retains certain requirements from AD 2011-18-52, revises certain requirements from AD 2011-18-52, and expands the applicability to include the newly-designed T/R blades. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective August 24, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2011-18-52, Amendment 39-17020 (77 FR 23109, April 18, 2012) (AD 2011-18-52). AD 2011-18-52 applied to Agusta S.p.A. (now Leonardo S.p.a.) Model AB139 and AW139 helicopters with a T/R blade part number (P/N) 3G6410A00131 or P/N 4G6410A00131 installed. The NPRM published in the Federal Register on May 10, 2021 (86 FR 24780). AD 2011-18-52 required, within 5 hours time-in-service (TIS), establishing a life limit of 600 hours TIS or 1,500 takeoff and landing cycles (cycles), whichever occurs first, on the affected T/R blades and updating the helicopter's historical records. If a T/R blade's total number of cycles was unknown, determining the T/R blade cycles by multiplying the T/R blade's hours TIS by 4 was required. For a T/R blade that, on the effective date of AD 2011-18-52, had already exceeded 600 hours TIS or 1,500 cycles, the AD required replacing the T/R blade with an airworthy T/R blade within 5 hours TIS.

AD 2011-18-52 also required, within 25 hours TIS, and thereafter at intervals not to exceed 25 hours TIS, inspecting the T/R blade for a crack or damage that exceeds the limits of the applicable maintenance manual. The inspection was required to be accomplished using a mirror, magnifying glass (5X or greater), and light source; or borescope. If there was a crack, or if there was damage that exceeded the limits of the applicable maintenance manual, AD 2011-18-52 required, before further flight, replacing the T/R blade with an airworthy T/R blade.

AD 2011-18-52 was prompted by a fatal accident involving an Agusta Model AW139 helicopter, which may have been caused by cracks in a T/R blade. EASA, which is the Technical Agent for the Member States of the European Union, issued EASA Emergency AD 2011-0156-E, dated August 25, 2011 (EASA AD 2011-0156-E) to require repetitive inspections and reducing the life limit of the T/R blades. According to EASA, this condition, if not detected and corrected, could result in failure of a T/R blade and subsequent loss of control of the helicopter.

After the FAA issued AD 2011-18-52, EASA issued a series of ADs as follows:

• EASA AD 2012-0030, dated February 17, 2012 (EASA AD 2012-0030), which superseded Emergency AD 2011-0156-E, advised that the manufacturer developed improved, newly-designed T/R blades P/N 3G6410A00132 and P/N 4G6410A00132, established life limits for each improved T/R blade, added repetitive inspections for the improved T/R blades, and advised that each T/R blade P/N had its own individual life limit.
• EASA AD 2012-0076, dated May 2, 2012 (EASA AD 2012-0076), which superseded EASA AD 2012-0030 and was issued after the manufacturer developed another version of improved T/R blades P/N 3G6410A00133 and P/N 4G6410A00133 with different materials. AD 2012-0076 required interim life limits for the new improved version of the T/R blades while also retaining the inspection requirements of EASA AD 2012-0030.
• EASA AD 2012-0076R1, dated July 13, 2012 (EASA AD 2012-0076R1), which revised EASA AD 2012-0076 after a modification was developed to allow installation of certain part-numbered T/R blades under certain conditions.
• EASA AD 2012-0076R2, dated February 20, 2014 (EASA AD 2012-0076R2), which revised EASA AD 2012-0076R1, was issued after another modification was developed. EASA AD 2012-0076R2 requires removing the 25 hours TIS inspection of certain part-numbered T/R blades, extending the life limit of certain part-numbered T/R blades, retaining the repetitive inspections of certain part-numbered T/R blades and depending on the inspection results, performing certain applicable corrections.

Also, after AD 2011-18-52 was issued, the FAA issued an NPRM (78 FR 54596), which published in the Federal Register on September 5, 2013. The NPRM proposed to require retaining the inspection requirements for certain part-numbered blades and expand the applicability to include the newly designed blades and establish life limits for those blades. The NPRM also proposed to require replacing any cracked blade or any blade that has reached its life limit. That NPRM was prompted by improved modifications of the T/R blades. However, because the FAA determined that the NPRM did not adequately address the identified unsafe condition, the NPRM was withdrawn on February 25, 2021 (86 FR 11477).

Additional review also revealed necessary changes to address the unsafe condition. Therefore, in the NPRM published in the Federal Register on May 10, 2021 (86 FR 24780), the FAA proposed to clarify the repetitive inspection for T/R blade P/Ns 3G6410A00131 and P/N 4G6410A00131 from, “visually inspect the T/R blade for a crack or damage” to “visually inspect the T/R blade for a crack and damage.” The NPRM further proposed to revise that repetitive inspection from “damage that exceeds the limits of the applicable maintenance manual” to “damage that exceeds allowable limits” to meet current publishing requirements. The NPRM also clarified the inspection area for that repetitive inspection by proposing to require using a figure in the related service information instead of using a figure in the body of the AD action. The NPRM also proposed to revise the requirements of AD 2011-18-52 by removing unnecessary information, including the special flight permits paragraph.

FMI: www.regulations.gov